Hi all,

I'm new to the forum and I'm going insane trying to fix an electrical problem with my 2008 FX2 Sport.

Tail lights are stuck on, even with truck powered off. They increase in brightness if the brake pedal is pressed.

Left turn signal goes solid when activated. The left tail light, mirror light, dash turn indicator, and front turn lights all go solid when it's activated.

Right turn indicator works normally.

Pressing the hazards causes all associated lights lock up solid, similar to what happens when the left turn is activated.

I've pulled the brake switch, fuses F02 and F06, changed the MFS, checked rear sockets for damage/corrosion, removed aftermarket trailer wiring, and repaired the rear ground (which was broken off) and the issue still persists.

Randomly while fiddling with the indicator and hazards the other day and leaving the truck running I was temporarily able to make the issue disappear and reappear. I powered the truck off with it in a 'working' state, but when I returned hours later it had gone wonky again.

Is it shorting somewhere? Is there an issue in the junction box?

I'm not the best with electrical problems so any and all help is much appreciated! Please let me know if I can provide more information that can help to diagnose the problem.

Thanks!

 

when many electrical gremlins come out at once, first thing to check (rule out) are the basics: battery, cables/connections, and grounds.

there are many grounds, but start with the ones under the cab kick panels, post pics of them. also, have battery/alt tested and ensure connections are clean and tight.

also, pull up mounting cover that is under drivers door when closed. inspect for water issues or cracked wires.

look under truck, under drivers seat, along frame, for black plastic junction box. is it filled with wet/mud?

report back with findings and/or any changes in symptoms.

 

Thanks very much for your input.

I was able to take a good chunk of photos. I know it’s rusty and salty. This truck has seen a lot of harsh winters. This also makes it tough to work on it outside right now. Let me know if these are helpful and where else I could look.


Rear ground that was broken off

New attached rear ground, I know it’s not perfect

Soldered wire attached to original ground running to rear harness near back bumper.

Behind plastic panel under driver door

Behind plastic panel under driver door

Another harness closer to cab above spare tire, not sure if helpful

Same harness as above.

Behind plastic panel under driver door

Behind plastic panel under driver door

Behind plastic panel under driver door

Behind plastic panel under driver door

Behind plastic panel under driver door

Ground under passenger junction box

Ground under passenger junction box

Wires and ground under passenger junction box

Junction box

Behind driver kick panel

Behind driver kick panel

Above pedals; brake switches

Under steering wheel, MFS connections

Above pedals and behind steering wheel

 

while probably not related to current issues, the FPDM is a problem waiting to happen. suggest buying replacement asap, and then when dealing with it, be SURE to find it’s ground (within about 6” of fpdm), and ensure that’s good too. google fpdm and/or read sticky thread on this forum


based on pics, i would focus on your ground by the fuse box and the rear one you already worked on.

? did someone spray a coating inside of body, by the fusebox ground? it looks like there is rust bubbling under costing just below ground. either way (coating or not), suggest removing ground and grinding down to clean metal and reattaching, move it up to solid metal if needed

the ground at rear, i’m sure is better than before, but not clear if you put on new connector or just wrapped wire around bolt? revisit this if any doubt… cover with silicone grease once you’re confident in it.

there is also a frame to body ground that i’m guessing will be compromised. look around wheel well area at front passenger wheel.

?what about battery/alternator/testing/connections?

 

Thank you for noticing that. While crawling around under there I did find the ground for the FPDM and it felt intact albeit rusty. I will add this to my list of things to look at and replace.

No coating was sprayed as far as I know, but it's definitely rust coming through from I guess the wheel well?

The ground at the rear is just a wire around a bolt. It was a very quick fix to try to remedy what I thought was the smoking gun. I intend to get a proper connector, but attempted to fix it with what I had in the moment. I'm not even sure where this ground is intended to connect to, I just connected it here as this is where the trailer wiring ground used to be connected (which I have removed once these problems started).

For the frame to body ground, am I looking inside the cab or from outside the truck?

As for battery/alternator etc. all I can say is battery is about a year old, but all connections are good as far as I can tell. The truck starts and runs completely fine mechanically. I disconnect the battery due to the lights draining it since this issue started about 10 days ago. I intend to get a multimeter to start probing, but not sure what exactly I should be looking for. I was unable to unplug the harness at the rear bumper, not sure if I'm missing a lock of some kind.

Again thanks for the input. I'm learning a lot experimenting with this truck but I'm still very new to automotive repair as a whole, and I've never had to deal with an electrical problem like this before.

I'm out of daylight, it's very cold, and I've got other obligations so I can't work on anything until at least tomorrow unfortunately.

 

sorry wasn’t clear: outside truck, wheel well. may help to turn when one direction (probably to left, but guessing from memory).

there have been a handful of threads (with pics) on this gen forum, so might try searching ‘frame body ground’ or similar terms.

 

Question are the license plate lights also ON?
As a trouble shooting step
Pull fuse F10. Did the the tail lights go OFF?
Report back

 

Just wanted to update where I'm at.

I removed all the plastic around the junction box kick plate to get a good look down there, and while there is quite a bit of rust at the bottom (as can be seen in the pictures I posted above) the spot where the ground is mounted is fine. I removed it, checked in and behind, even sanded it down and added dielectric grease just in case but no changes unfortunately.

I was able to find the ground in the passenger side wheel well, and it's connected and intact, but quite corroded. I ran out of daylight when I got to this point so will try cleaning it up today. I can also post more pictures if it might be helpful for others for what I'm seeing and what I've adjusted so far.

I forgot to mention my top/overhead brake light was also not working, but when I pulled it apart it just appeared the bulb was burnt out (quite black and filament dislodged). I'm assuming this is totally unrelated but thought I'd mention it just in case.

Jimboy I'll check this out and report back. I want to say they're not on, but I'll give it a look. Should they be on at all times or only when the lights are turned on?

I've pulled fuse 6 and 2 believing those to be the fuses for the circuits giving me issues, but both times the lights remained on. I'll pull fuse 10 and report back.

 

I'll also add a few more notes while I'm thinking of it in case it gives more hints as to what is wrong:

There used to be an aftermarket trailer harness installed. This truck did not come factory with the trailer tow package as far as I know (I bought it second hand from a family member).

Behind the rear harness, there's a branch that comes off the main loom (It appears to be factory) that the aftermarket trailer harness was tied into. Whoever had installed it also tied a wire from this point up to my rear right tail light, that had an in-line 15amp fuse, and was spliced into the orange/blue line. I have since removed all these wires.

I soldered and restored the orange/blue wire at the tail light to factory, removed the tow harness, cut back the ends of the factory wires where they connected to the harness, and heat shrinked the ends to ensure they're not touching and protected.

Again I do have some pictures of this stuff but not a ton.

I'll keep tinkering with what's been suggested and report back.

 

The license plate lights are not on. They went on normally when I switched the lights on. Powered off again once I switched it off.

Pulling fuse F10 did not solve my problem, but I decided to start pulling other fuses.

When I got to F13 (Climate control module power, flasher relay) they shut off. When I plugged this fuse back in, the lights remained off. My turn functions and hazards all functioned normally, and everything appeared good. I was on low fuel so drove to the gas station. When I turned the truck off and went out to fuel the lights were stuck on again. Once I got back in sure enough my turn signal was also borked again. I drove back to the house and parked but kept the truck running. After sitting for a few minutes and touching NOTHING I noticed they had once again shut off, and turn signal/hazards back to normal. Is this textbook bad ground? Or is it a harness issue? I’m sure if I leave the truck sitting it will come back again.

Appreciate all the input!